1. Field of the Invention
The present invention relates to an exhaust device for a motorcycle. More specifically, to an exhaust throttle valve arrangement structure advantageous to disturbance due to scattered stones or the like.
2. Description of Background Art
An exhaust throttle valve is known that is provided in the exhaust system of an engine to adjust an amount of exhaust flow according to operating conditions, thereby intending to reduce exhaust noise and to provide high power.
Examples of the provision of such an exhaust throttle valve include one in which the exhaust throttle valve is provided at a collecting portion disposed forward of an engine is disclosed in Japanese Utility Model Publication No. Hei 4-20983. In addition, another example of an exhaust throttle valve is provided at a collective exhaust pipe located near the front end of a muffler See, for example, Japanese Patent Laid-open No. Hei 4-292534.
Since the exhaust throttle valve is provided in the exhaust system, it is sometimes disposed close to a front wheel or a rear wheel or on the vehicle body lower portion close to the ground surface. If the exhaust throttle valve is located at any one of such positions, it tends to undergo a disturbance due to the scattered of stones or the like.
For Japanese Utility Model Publication No. Hei 4-20983, a rotational arm or drive wire of the exhaust throttle valve is located on the lateral surface of a collective portion forward of the lower portion of an engine, that is, located rearward of and close to the front wheel. Thus, stones or the like scattered by the front wheel tends to cause a disturbance.
For Japanese Patent Laid-open No. Hei 4-292534, the drive portion or the like of the exhaust throttle valve is exposed to the vicinity of the front end of the muffler located laterally of the rear wheel. Thus, it is desirable to provide a structure that protects it from being disturbed due to stones scattered by the front wheel or the rear wheel.
In addition, it is desired that the structure for protecting such a component from disturbances due to scattered stones or the like be realized as simply as possible. Accordingly, an object of the invention is to meet such a desire.